How to enable only some specific dates from datepicker using Jquery/Javascript

I need to enable some specific future dates as per the user input day from Jquery datepicker using Jquery/Javascript. I am explaining my code below.

<strong>Select Date:</strong>
<input type='text' id='txtDate' />
<button class="process" id="btn" onclick="duplicate();">Clean</button>
<script type="text/javascript">
    $( "#txtDate" ).datepicker({
        changeMonth: true,
        dateFormat: 'dd-mm-yy',
        minDate: 0,
    });
    function duplicate() {

    }
</script>

Here I have jquery datepicker. Suppose I need to enable all future Monday and Thrusday dates only and other dates will remain disabled.